Dry dust filter for using in operations endangered by gases

ABSTRACT

The invention related to dust filters ( 1 ) which are especially used in operations endangered by gases and comprise filter elements ( 10 ) rendered antistatic by means of derivative constituents such as carbon fibres, salts or special steel fibres ( 26, 27 ). The filter material ( 10 ) is connected to the housing frame ( 14 ) by use of conductors ( 16 ), bypassing the seal ( 15 ), in such a way that a negative electrical charge of the inner chamber of the individual filter element ( 10 ) or the dust filter ( 1 ) is avoided.

This application claims the benefit of German Application No. 103 03798.5 filed Jan. 31, 2003, German Application No. 103 57 684.3 filedDec. 10, 2003 and PCT/DE2003/004271 filed Dec. 24, 2003, which arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to a dry dust filter for application in operationsendangered by gas, in particular in underground mining and tunnelconstruction, the dust filter including a housing, in which one or moredust absorbing filter elements are provided through which filterelements the dust containing air current flows, the filter elementshaving a dust retaining filter material and/or are suitably designedtherefore.

Such dust filters, also known as dry filters, are applied in differentindustrial fields, in order to settle dusts created in recovery orproduction processes as early and extensively as possible and therewithto remove such dust out of the airflow. Filter elements are accordinglyarranged in a housing mostly made of metal, the filter elementsconsisting of filter cloth or a suitable knitwear or other similarmaterial, through which the airflow passes so that the alter elementsretain the dust during through-flow resulting in purified air flowingout through the outlet side of the housing.

These filter elements are cleaned by beating, counter flow or similarmeasures, whereby the dropping dust is collected and disposed of. Inoperations endangered by gas the air current has to be reduced to suchan extent that, on impact of corresponding dust particles or otherparticles taken along by the air current, no sparks are created.Therewith the through-flow of such de-dusters or dust filters is reducedstrongly and large plants have to be acquired or other methods forde-dusting have to be searched for.

Especially in operations endangered by gas and thereby in particular inunderground mining, also no materials, which impair the remaining plantsand in particular the filter self rescue devices, which have to protectworkers in these operations, must be released. Such detrimental effectsin particular can enter into the environment especially during glowingof parts of the filter elements or when burning, whereas the regulationsprovide that no toxic or adhesive residue gases are to be released intothe environment. The plants, which are installed there, have to bedesigned correspondingly. In the U.S. Pat. No. 5,868,807 a dust filterwith usual filter elements with wire mesh support is described. Thecrude gas has to pass a layer of fine grain material prior to reachingthe filter elements. Nothing is mentioned about applicationpossibilities in operations endangered by gas and the prevention ofelectrostatic charges. The honeycomb structure of the arrangementaccording to the U.S. Pat. No. 5,259,190 A is provided for the ignitionof gas or the combustion of carbon dust. In the filter for diesel powermachines according to WP93/13303 the filter bodies are joined to anenergy supply. Nothing is said about preventing electrostatic charges.

SUMMARY OF THE INVENTION

The invention therefore has as object to create a dry dust filter, whichalso can be applied in operations endangered by gas and thereby cause noharm for self rescue devices applied underground.

The object of the invention is achieved thereby that a gas impermeableseal is provided between the housing, consisting of sheet metal or thelike electrically conducting material, and the edge of the filterelement a gas impermeable seal hindering or preventing the exit ofharmful materials out of the housing is provided and that the filtermaterial is designed to be electrically conducting and is connected bymeans of an electrical conductor bypassing the seal to the housing sothat from the inside of the edge a conducting connection with thehousing frame made of metal is provided.

Thereby it is possible to apply such dust filters and de-dustersconsisting thereof surprisingly safe and in simple manner also inoperations endangered by gas, without that the danger exists thathazards due to electro-static charging or the like can result. Even thenif a fire should arise, damaging materials initially cannot escape fromthe housing. However, should this happen to a lesser degree, then theemerging gases cause no harm to the filter self-rescue devices so thatalso in extreme cases an endangerment of the persons active in thisoperation or the region does not exist. It is ensured that small dustparticles contacting the filter elements cannot create an electricalcharge because the filter element itself is electrically conductive andthe created electrical currents are conducted further by way of theelectrical conductor so that they reach the housing made of sheet metaland here become harmless due to the particular embodiment of therespective filter element and the de-duster produced thereof. Thehousing, consisting of sheet metal, is either earthed somehow or, due tosuitable distribution the electrical currents are completely harmless.Thus also a possible ignition is substantially avoided.

According to a further suitable development of the invention it isprovided that the filter element is joined to the housing by way of theholder elements projecting beyond the inside of the filter element, andthe electrical conductor is conductively connected thereto and to thefilter material. The filter element as a rule is attached by way ofmounting screws or by way of similar elements to the housing, in orderto provide for an exchange of these filter elements. If the filterelement itself is not attached to the housing, but to a partial framedisplaceable or otherwise attachable in the housing, then in any case itcan be ensured that by means of the invention the electro-staticcharging of the overall element is reliably avoided. When screwing themounting elements the electrical conductor is fixed, which is itself inelectrical contact with the electrically conducting filter material sothat the described problems cannot occur when dust particles impact athigh speed onto the filter material. This, as already is in the caseregarding the basic invention, has the enormous advantage that no carehas to be taken regarding the air led through the housing. In fact, theoptimum speeds can be applied, which ensure an optimum use of thede-duster or dust filter.

A further suitable embodiment provides that the electrical conductor isdesigned as copper wire strand and does not block the filter material orthe filter self-rescue device in case of fire. Accordingly, on the onehand, a simple realization of the transfer of the electrical charge isensured and simultaneously it is achieved that even in an extreme case,that is with fire, an endangerment of the important filter self-rescuedevices does not occur. Such a material is also referred to as ATEXmaterial.

The electrical conductor, preferably designed as electrical conductor ofcopper wire strand, is, according to a further embodiment, wavy andencloses the filter material and leads to the end pieces of holderelements. The electrical conductor therewith abuts tightly against thefilter material so that a discharge is in any case ensured, inparticular because the filter material is included in the electricalconductor. The communication to the housing of sheet metal via theholder elements is created by means of the electrical conductor with itsend pieces.

A sliding of the end pieces of the electrical conductor off the holderelements is prevented thereby that the end pieces have loops embracingand being displaceable on the threads of the holding elements formed asscrews. Thus it is only necessary to push the corresponding loop shapedend pieces over the threads of the holder elements and then to apply thenuts so that then the electrical connection is in any case ensured.

It already has been stated above that the filter material is to beenclosed by the electrical conductor. Thereby it is providedcomplementarily that the electrical conductor is joined to the filtermaterial at several positions. As a rule it is sufficient if the filtermaterial is suitably tightly enclosed by the electrical conductor. Theinvention provides that the electrical conductor with the filtermaterial is joined conductively at several positions in order to ensurethat, during corresponding shaking movements or other loads, the tightcontact between electrical conductor and filter material is ensured.

The creation of electrical charges is avoided by suitable filtermaterial, whereby the invention here provides that the filter materialis coated or is drenched with anti-static material and that theconnection of the surface of the filter material is formed permanently.Thereby, by way of this embodiment it is ensured that the filtermaterial achieves its actual object, namely to remove the dust particlesfrom the air current and to render these particles “harmless”. Filtermaterial coated with anti-static material can be produced by way ofpresent day technology, in that anti-static material, for example in theform of a salt, is applied to the actual filter material or filtercloth. Thereby it is ensured that it is not separated from the filtermaterial by the air current, in the case of moist or even water dropletstaken along by the air when, however, special precautions are necessary,which prevent or exclude the occurrence of such water constituents.Thereby the dust particles are bound reliably by the filter materialbecause, according to a further development, it is provided that thefilter material has a coating, which forms a not-easily inflammableanti-static, microporous foam membrane, which is arranged on the onflowside. By means of the microporous design of the membrane it is ensuredin particular that the air passes through the filter material and isdischarged as purified air.

The optimum micro-porous design of the foam membrane is achieved inparticular if the coating is an acrylate foam or PU foam, to which sootor to graphite is admixed.

The conductivity is achieved in particular thereby if, or is given tothe filter material, the carbon fibres, salts or special steel fibresare bound into the filter material. Thus conducting components can bereliably brought into contact with the actual filter material in orderto ensure the overall anti-staticness of the overall structure.

A filter material, which does not detrimentally influence the filterself rescue device, also in extreme cases, that is during fire, is thatwhich is formed as polyimide needle felt with support fabric. Thisfilter material furthermore advantageously is self-supporting whereasthis characteristic can be enhanced by additives. For this purpose it issupplementally provided that receptors, providing the self-supportingcharacteristics, are added to the filter material, whereby theself-supporting characteristic is supported by way of folding or similarmeasures. Thereby there results advantageously a fabric, which does notneed a frame, which thus can be self-supportingly pushed into theprescribed position in order to fulfil its purpose there, whereby thefunction can be improved further by way of characteristics mentionedhereafter.

The stiffening of the filter material by means of receptors is supportedby way of a further development in that the edge of the filter elementwith the filter material is produced of a material PU-sealing compoundwith content, which is not easily inflammable and the filter material isdesigned circumferential or additionally supporting head and foot sideor with a filter element head and filter element foot. Therebyadvantageously there results an overall stiffened element, which can bepushed reliably into the working position and from there can also beexchanged, if found to be necessary during cleaning of the individualfilter elements. In particular the micro-porous foam membrane alreadymentioned leads to de-dusting degrees of optimum values, whereby 0.1mg/cm³ can be achieved without problems by way of such filter elements.

If air containing larger quantities of moisture are supplied to thehousing, then the invention provides that the filter housing has afilter entry with a connection flange, which is designed correspondingto a coupling flange of an associated pre-separator, which is providedwith separator profiles formed to be flow favourable and designed toseparate water droplets and aerosols. The invention provides, stated insimple terms, that the moisture constituents are removed from the aircurrent flow at an early stage and this being not by heating, but infact thereby that separator profiles are placed into the air current,which remove the water droplets and aerosols from the air current.Naturally still a part of the dust in the form of slag will be carriedout but this is not disadvantageous but in fact is advantageous becausethereby the subsequent actual dedusting parts are relieved. These waterdroplets or aerosols and the corresponding liquid or the slag arecollected at or in the pre-separator and then are disposed of.

A reliable separation of the water droplets and aerosols is achieved inaccordance with the invention in particular thereby that a baffle withangle profiles is arranged upstream of the separator profiles, wherebythe separator profiles have noses projecting counter to the flowdirection of the air or the dust containing air and forming a type ofpocket. By means of these baffles simultaneously also too largedimensioned dust particles are separated so that the subsequentseparator profiles and, behind them, the filter elements aresimultaneously protected. The baffles with angle sections are connectedto the slag pump and the collection parts of the separator profiles sothat both simultaneously receive a waste disposal.

Due to the unavoidable contamination a continuous operation of the dustfilter or the de-dusters is ensured because the separation profiles andthe angle sections of the baffles are provided with a supply tube andare arranged upstream of water nozzles discharging in flow direction ofthe air. The water nozzles, for example, are stopped during stopping ofa tunnelling machine or other dust creation machines and ensure thatboth the separator profiles as well as the angle profiles of the bafflesare freed of sticking dust and therewith are again fully functionallyavailable for the following operation.

It is described above that the electrical conductor is to be providedenclosing the filter material independently of the filter frame,whereby, according to a further development, it is also provided thatthe electrical conductor is integrated into the filter material withsupporting edge, contacting the filter material and with end sideconnection positions for the holder elements. Thereby the possibility isgiven to introduce the electrical conductor as such immediately into theprotection of the filter frame whereby by a two part formation of thefilter frame or similar measures during the fixing of the filtermaterial also the electrical conductor is simultaneously fixed, so thatit secures the conductance of charges because, on the one hand, it hasthe connection parts for the holder elements, thus securing theelectrical connection out of the filter frame.

The seals applied must be gas impermeable and additionally also elasticto produce the requited sealing effect. Thereby the invention provides,different to the embodiment described before, between the housingconsisting of sheet metal or other electrically conducting material andthe edge of the filter element, a gas impermeable seal, which is joinedto the electrically conducting filter material and itself can beelectrically conducting or be coated with such an elastically formedmaterial. In particular the embodiment with the electrical coatingprovides the possibility to ensure the requited sealing effect byelasticity whereby this solution is applicable and suitable inparticular if the dimensions, in particular of the gas impermeable seal,are relatively large.

The invention is characterized further thereby that a filter element ora dry filter with suitable filter elements is created, which also can beapplied in safety relevant operations endangered by gas. The inventiontherefore is particularly advantageous because a de-duster is madeavailable, which can be applied both in normal operations and also inoperations endangered by gas, but which also can be applied in suchoperations, which at times are endangered by gas and then again have anormal operation. Thereby the expense incurred for allowing suchapplications is as low as possible because the constructional form ofthe filter element and the overall dust filter can be retained. It ismerely necessary to provide a connection between the housing made ofsheet metal and the corresponding filter elements, which is possible inelegant and simple manner. Thereby the discharge of correspondinglylarger or smaller filter surfaces possible because the electricalconductor applicable does not engage only in spots but also ensures thatan area “discharge” is achieved. Simultaneously it is emphasised asbeing essential that the electrical conducting filter materialapplicable also does not endanger filter self-rescue devices applicablein case of fire in underground mining or in similar other operations,that is due to the released fire residues and gases these filterself-rescue devices cannot be blocked and therewith tenderedineffective. In fact the filter rescue devices also remain operative insuch extreme cases and therewith can lead the carriers of such filterrescue devices also into regions, which are safe. It is furthermoreadvantageous that even then if actual problems occur within the dustfilter, these are sealed such that endangering gases cannot emergetherefrom or also be made harmless therein. Here the electricallyconducting filter material assists to reduce further danger or toprevent it. It finally is advantageous that the filter elementsthemselves also can be developed further such that they are simple to bemounted because, for example, a filter frame is not required any longeror can be handled simply, because it has the required self-stiffness andby way of suitable coatings its effectiveness can be increased andimproved and therewith very good values can be achieved.

Further details and advantages of the object of the invention resultfrom the subsequent description of the associated drawing, in which apreferred example of an embodiment with the details and individual partsnecessary therefore is illustrated. It is shown in:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a dry dust filter with filter elements in side view,

FIG. 2 a section through the dry dust filter shown in FIG. 1 with afilter element,

FIG. 3 an individual filter element with connection of the edge and thehousing,

FIG. 3 a a filter material with a coating,

FIG. 4 an electrical conductor in side view,

FIG. 5 a pre-separator in side view associated with the filter accordingto FIG. 1 and

FIG. 6 a pre-separator in plan view and partially without cover.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a dry dust filter in side view, whereas this is composed ofseveral individual elements. The overall unit can be supported on thefloor or can be suspended by way of the hooks shown on the upper side tosingle suspension tail or other constructional parts. The housing 2 ofall of the individual units is identical, whereby at the filter inlet 3a coarse screen 5 for a pre-dusting takes care, that is here the coarseparts are removed from the onflowing air. The flow direction isindicated by 4;

The filter inlet 3 has a connection flange 6, which allows the flangingon of a pre-separator, which is explained further hereafter.

The filter outlet 7 forms the rear end of the housing 2, whereby the drydust filter 1 shown here represents only one embodiment. In the housingshown here the purified air emerges from the filter outlet 7. In thehousing 2 a multiplicity of filter elements 10 are arranged. These arecleaned in regular time intervals, whereby the dropping down dust dropinto the removal conveyor 8, which cares in intervals for a removal ofthe dust. Also other collection aggregates and waste removal parts arepossible.

FIG. 2 shows a section through the housing 2 with a filter element 10arranged therein. This filter element 10 has a circumferential edge 11,which is fixed on the wavy cloth shaped filter material 12. Dustcontaining air flow flows through this air, which then escapes by way ofthe clean gas channel 13 leaves the housing 2 of the dry dust filter 1.It is only indicated that a seal 15 is situated between the edge 11 andthe housing frame 14.

This region is shown enlarged in FIG. 3, whereby it can be seen that theedge 11 surrounds the filter material 12 or represents the edge of thismaterial.

The seal 15 is housed in the connection region with the housing frame 14between this and the edge 11, for example in a sealing groove which iscircular in diameter or similarly formed elastic sealing bead, which, onpressing together of the housing frame 14 and the filter material, takescare of a gas tight closure. This seal 15 prevents that electrostaticcharges are removed in the region of the cloth shaped filter material 12and are made harmless. FIG. 3 shows that, for removal of such charges,an electrical conductor 16 is provided, which encloses the filtermaterial 12 and is joined to the holder elements 18, 19 consisting ofmetal. For this purpose the end pieces 22, 23, seen from FIG. 4, areprovided with a loop 24, which is pushed over the thread 20 andtherewith allows a fixing by way of nuts not shown here. The screw head21 and the thread 20 or this part of the holder element 18, 19 formed asscrew allows precisely that from the inner side 17 of the edge 11 aconducting connection to the housing frame 14 made of metal is achieved.

FIG. 4 explains that this electrical conductor 16 encloses the filtermaterial 12 circumferentially and takes care that always a conductanceis ensured, also if only a partial charging of the filter material 12takes place. The embodiment of the electrical conductor 16 shown in FIG.4 is a copper strip 25.

The filter material 12 shown in FIG. 3 is an ATEX suitable material,which also cannot block filter self-rescue devices even if a fire shouldoccur. The anti-static receives this material in particular in theexample shown by application of an anti-static material in the form of asalt, by way of carbon fibres or special steel fibres 26, 27.Correspondingly FIG. 3 shows in section whereby the special steel fibres26, 27 are merely indicated. In flow order to prevent a dissolution ofthese salts in case of moist air or air containing water droplets, apre-separator 28 can be provided upstream of the housing shown in FIG.1, which can be seen in FIG. 5 and FIG. 6. This pre-separator 28 or itshousing has a copper flange, which is shaped corresponding to theconnection flange 6 of the housing 2 so that an easy assembly anddisassembly is possible.

The pre-separator 28 centrally has, as shown in FIG. 6, a multiplicityof pre-separator profiles 30, which are provided with noses 31, whichform a type of pocket 32. These pockets 32 are open counter to the flowdirection of the air so that during onflow the water droplets andaerosols contained therein are collected and are precipitated. The slagor the water collected thereby is supplied by way of a collection tube39 to the pump connection 40, thus can be disposed thereby.

A baffle 33 with angle profiles 34 is provided upstream of the separatorprofile 30, by way of which profiles the coarse dust or coarseconstituents in the air flow can be separated and also be disposed of byway of a collection tube and the pump connection 40, which is the sameas for the separator profile 30. Discharge tubes 35, 37 with waternozzles 36, 38 are arranged upstream of both the separator profiles 30as well as the angle profiles 34 whereby these water nozzles 36, 38 areadjusted such that they spray clean water in flow direction for into theseparator profiles 30 or angle profiles 34 so that cleansing isachieved. This slag containing water is also discharged by way of thecollection tube 39 and the pump connection 40.

The seal 15 shown or indicated in FIG. 3 itself also can be conductivefor which purpose an additional reference numeral 45 is introduced.Furthermore the edge 11 can be joined directly or by way of a connectionpart 44, as shown in FIG. 3, to the housing frame 14 or to the housing2. The filter element head 41 and the filter element foot 43, accordingto FIG. 4, are made of plastics material, which facilitates the pushingin of the individual filter elements 10. In FIG. 3 a it is merelyindicated that a filter material 12 can also be provided with a coating42, for example a coating of acryl foam or PU foam, which is difficultto ignite, antistatic, micro-porous and can be processed well. Thisfoam, being the coating 42, 42′ lies on the corresponding filtermaterial 12, whereby a discharge channel is indicated by 50 by way ofwhich the cleaned air can flow out. Due to the coating 42 very highseparator degrees can be achieved. 0.1 mg/cm³ can be achieved.

Receptors are not shown, which lead to the stiffening of the filtermaterial 12. These are supplied in order to stiffen the overall filterelements so far that a filter frame is not required but that aself-stiffening element is available. The filter element head 41 and thefilter element foot 43 facilitate this.

1. Dry dust filter for application in operations endangered by gas,comprising a housing (2), in which one or more dust absorbing filterelements (10) are provided through which filter elements the dustcontaining air current flows, the filter elements having a dustretaining filter material (12), characterized thereby that between thehousing (2), consisting of sheet metal or another electricallyconducting material, and an edge (11) of the filter element (10) a gasimpermeable seal (15) hindering or preventing the exit of harmfulmaterials out of the housing (2) is provided and that the filtermaterial (12) is designed to be electrically conducting and is connectedby means of an electrical conductor (16) bypassing the seal (15) to thehousing (2) so that from the inside (17) of the edge (11) a conductingconnection with the housing frame (14) made of metal is provided.
 2. Drydust filter according to claim 1, characterized thereby that the filterelement (10) is joined to the housing (2) by means of holder elements(18, 19) projecting beyond the inner side (17) of the filter element(10) and the electrical conductor (16) is conductively joined theretoand to the filter material (12).
 3. Dry dust filter according to claim1, characterized thereby that the electrical conductor (16) as copperstrip (25) and the filter material (12) are designed not to block afilter self-rescue device in case of fire.
 4. Dry dust filter accordingto claim 1, characterized thereby that the electrical conductor (16) isdesigned to include the filter material (12) and showing end pieces (22,23) leading to holder elements (18, 19).
 5. Dry dust filter according toclaim 4, characterized thereby that the end pieces (22, 23) enclose athread (20) of the holder elements (18, 19) and have loops (24)displaceable thereon.
 6. Dry dust filter according to claim 1,characterized thereby that the electrical conductor (16) is joinedconductively to the filter material (12) at several positions.
 7. Drydust filter according to claim 1, characterized thereby that the filtermaterial (12) is coated with anti-static material and/or is drenchedtherewith and that the connection is formed pressing the surface of thefilter material (12).
 8. Dry dust filter according to claim 7,characterized thereby that the filter material (22) has a coating (42),which forms a non-flammable anti-static micro-porous foam membrane,which is not easily flammable and is arranged on the flow side.
 9. Drydust filter according to claim 8, characterized thereby that the coating(42) is an acrylate foam or PU foam, to which soot or graphite isadmixed.
 10. Dry dust filter according to claim 1, characterized therebythat carbon fibres, salts or special steel fibres (26, 27) are includedin the filter material (12).
 11. Dry dust filter according to claim 3,characterized thereby that the filter material is formed as polyimideneedle felt with support fabric.
 12. Dry dust filter according to claim1, characterized thereby that receptors providing self-supportingcharacteristics are added to the filter material (12), whereby theself-supporting characteristic is further supported by folding.
 13. Drydust filter according to claim 1, characterized thereby that the edge(11) of the filter element (10) is produced with the filter material(12) of a PU grout material with content, which is not easily flammable,and the filter material is formed circumferential or supporting a footand head side additionally or forming a filter element head (41) andfilter element foot (43).
 14. Dry dust filter according to claim 1,characterized thereby that the housing (2) has a filter inlet (3) with aconnection flange (6), which is formed corresponding to the couplingflange (29) of an associated pre-separator (28), which is provided withseparator flow favorable profiles (30) and thereby waterdrops andaerosols are separated.
 15. Dry dust filter according to claim 1,characterized thereby that a baffle (33) with angle profiles (34) isarranged upstream of separator profiles (30), whereby the separatorprofiles (30) have noses (31) projecting counter to the flow direction(4) of the air or the dust containing air and forming a type of pocket(32).
 16. Dry dust filter according to claim 1, characterized therebythat a supply tube (35, 37) is allocated to separator profiles (30) andangle profiles (34) of baffles (33) and water nozzles (36, 38) directedin flow direction (40) of the air are arranged upstream of the separatorprofiles.
 17. Dry dust filter according to claim 1, characterizedthereby that the electrical conductor (16) is contacting integrated inthe filter material (12) with supporting edge (11) and has connectionparts (44) for the holder elements (18, 19) at the end side.
 18. Drydust filter for application in operations endangered by gas, comprisinga housing (2), in which one or more dust absorbing filter elements (10)are provided through which filter elements the dust containing aircurrent flows, the filter elements having a dust retaining electricallyconducting filter material (12), characterized thereby that between thehousing (2), consisting of sheet metal or another electricallyconducting material, and the edge (11) of the filter element (10) a gasimpermeable seal (15) is provided, which seal is joined to theelectrically conducting filter material (12) and itself is designed tobe electrically conducting or is coated by means of an elasticallyformed, electrically conducting material.